A multicast broadcast service (MBS) is a point-t multipoint (PTM) service for transmitting data from one source to a plurality of receivers. This MBS transmits the same data to the plurality of receivers over a common radio frequency (RF) channel in order to effectively use radio resources.
In a general wireless access system, the MBS can be classified into two types of MBSs, i.e., a first-type MBS and a second-type MBS. The first-type MBS is a single-BS access scheme, such that data is provided by one base station in one cell. The second-type MBS is a multi-BS access scheme, allows several base stations to make a single MBS zone, such that the base stations provide the MBS service within the single MBS zone. In other words, the second-type MBS receives the same burst from an MBS server in several cells contained in the same MBS zone using a single MBS zone ID, such that it provides the MBS service using the received burst. Therefore, although a mobile station moves among cells having different base stations, this mobile station can acquire service continuity and a macro-diversity gain without performing a handover from one base station to another base station.
FIG. 1 is a conceptual diagram illustrating a reference model of an MBS for use in a broadband wireless access system.
Referring to FIG. 1, an MBS network includes a media server, an MBS distribution server, one or more base stations (BSs), and one or more mobile stations (MBs). This MBS media server provides the base stations with MBS data, and performs distribution of MS authentication and encryption keys associated with MBS contents. The MBS distribution server performs scheduling of MBS data transferred to several base stations (BSs). Optionally, the MBS distribution server may be omitted, and the MBS contents server may perform scheduling of the MBS data. The base station receives MBS data over a backbone network, and transmits the received MBS data to the mobile stations via a radio interface, and the mobile station receives the MBS data from the base station.
The MBS of the broadband wireless access system has the following features 1)˜4).
1) Minimized-Power Consumption:
A mobile station can minimize an amount of power consumption while receiving MBS data, irrespective of a current operation mode (e.g., a normal-operation mode, a sleep mode, and an idle mode).
2) Mobility:
The mobile station is able to receive a seamless MBS connection while in motion among base stations.
3) MBS zone:
MBS contents are transferred via different MBS zones which are locally distinguished. MBS setup information (e.g., MBS connection ID, an encryption key, and a service ID) can be differently constructed in different MBS zones.
4) Security:
The MBS contents can be transferred to only authenticated users. An encryption key of a MAC PDU of MBS data can be equally applied to individual base stations contained in the MBS zone.
Next, the MBS zone will hereinafter be described in detail.
MBS-associated parameters (e.g., a security key and a multicast connection ID) may be differently established according to individual zones. The MBS contents can be broadcast in only a restricted zone. Therefore, when the mobile station receiving the MBS contents moves from one zone of one base station to another zone of another base station or is handed over from one base station to another base station, the mobile station must determine whether or not the stored MBS data is valid, and must determine whether or not it is able to continuously receive MBS contents.
Presently, if the base station provides the MBS via parameters different from those of MBS information owned by the mobile station, or does not transmit the MBS contents, the mobile station must access a new base station in order to update parameters associated with the MBS contents. In order to solve the above-mentioned problem, a broadband wireless access system manages the MBS zone in which one or more MBS provision base stations are grouped.
The base stations contained in the same MBS zone transmit the MBS contents to the mobile stations using the same MBS parameters. Also, the base stations transmit an ID of the MBS zone to the mobile station, such that this mobile station can recognize the MBS zone using this MBS-zone ID. The mobile station can immediately recognize whether or not the MBS parameter is valid using an MBS-zone ID received from the base station.
Also, if the mobile station moves to a zone of another base station within the same MBS zone, there is no need to perform a procedure for re-establishing MBS-associated parameters in order to receive MBS data. Also, the base stations contained in the same MBS zone transmit the MBS data using the same radio resources at the same time, such that MBS-data reception efficiency of the mobile stations can be increased by a Macro-diversity effect.
Operations for minimizing the amount of power consumption of the mobile stations receiving the MBS data will hereinafter be described in detail.
The mobile station can reduce the amount of power consumption during the reception time of MBS data, irrespective of current operation modes (e.g., a normal-operation mode, a sleep mode, and an idle mode).
Generally, a downlink MAP information element (DL-MAP IE) contained in a downlink MAP (DL-MAP) message is defined to indicate a burst transferred in a current frame. However, in order to receive the broadcast-formatted burst, the mobile station receives the DL-MAP message for each frame, and must decrypt the received DL-MAP message. In this case, the amount of power consumption cannot be decreased.
However, the MBS MAP information element (MBS_MAP IE) informs the mobile station of the number of frames needed until transmitting the MBS-data burst, such that the mobile station may not decrypt a downlink frame including the DL-MAP message in association with a frame to which MBS data is not delivered. As a result, the mobile station can minimize an amount of power consumption. Specifically, the MBS_MAP IE can greatly reduce an amount of power consumption in a sleep-mode MS and an idle-mode MS. Scheduling information of the MBS data burst can be transferred via the MBS_MAP IE acting as one of DL-MAP IEs, and can also be transferred in the form of the MAC management message such as the MBS MAP message.